Sickle cell anemia

A hemoglobinopathy that is due to homozygosity from a point mutation in the beta-globin gene, where ultimately the glutamic acid (a hydrophilic residue) on position 6 of the beta globin chain is replaced with valine (a hydrophobic residue). The hydrophobic residues are not well suited for the surrounding hydrophilic environment inside the RBC and ultimately lead to aggregation of these abnormal hemoglobin molecules . These "polymerized" hemoglobin molecules cause abnormal RBCs with rigid and sickled shapes. Sickle cells lack the flexibility of normal RBCs and can be trapped within capillaries causing multiple complications (e.g. "sickle cell crisis" which includes vaso-occlusive crisis, hemolytic crisis, aplastic crisis, and sequestration crisis). Sickle cell patients commonly undergo autosplenetcomy during childhood due to infarction of the spleen with subsequent increased risk for developing infections due to encapsulated bacteria such as Streptococcus and H. influenzae, therefore requiring vaccinations. Various other clinical complications include stroke, avascular necrosis, osteomyelitis (Salmonella infection), chronic pain, pulmonary hypertension, chronic renal failure, and etc.